Apparatus for controlling the firing of an explosive charge



May 12., v19'70 F. A. HESTER, JR

APPARATUS FOR CONTROLLING THE FIRING OF AN EXPLOSIVE CHARGE Filed Nov.18, 1943 .4 Sheets-Sheet l III! r. M H.

Frank Gttorneg Mayv 12., 1970 F. A. HESTER, JR 3,511,132

APPARATUS FOR CONTROLLING THE FIRING OF AN EXPLOSIVE CHARGE Filed Nov.`18,1945 .4 sheetssheet 2 Zsnventor Cttorneg .May 12, `19701 F. A.HEsTER, JR 3,511,132

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MgylZ., 1970 F. A. HEs'rER, JR

APPARATUS FOR CONTROLLING THE FIRING OF AN EXPLOSIVE CHARGE 4 Filed NOV.18, 1945 .4 Sheets-Sheet 4 l'aa /aa FBF. (76255 PEI? 5661 :inventor mkg@Fran/Z.

Gttorncg Uhitedr States Patent O U.S. Cl. 102-70.2 14 Claims Aus'TRl/wroF THE Ds'cLosURnV This invention relates to apparatus for and a methodof controlling the firing of an explosive charge, and more particularlyto an apparatus and method of this type which are especially suitablefor submarine use.

In submarine operations, it is sometimes necessary to set off `anexplosive charge for destroying a target located below the surface ofthe water. For example, in naval warfare, the problem of destroyingsubmarines after they have been located is an exceedingly important one.Various attempts have been made heretofore to lire explosive chargeswhich have been directed toward submarines so that they will producemaximum damage to the submarines. Obviously, this can only be done ifthe explosive charges` are detonated or fired when they are in closeproximity` to their targets. In this respect, however, the prior artmethods of and devices for controlling the firing of depth charges havenot been very successful.

It is the primary object of my present invention to provide an improvedmethod of and apparatus for ring depth charges in a manner which willnot be subject to the limitations of those of the prior art.

More particularly, it is an object of my present invention to provide animproved method of and apparatus for controlling the tiring of depthcharges so that such charges will not explode until they have reached aminimum distance from the target.

Another object of my present invention is to provide an improvedapparatus as aforesaid which will be protected against tiring inresponse to countermine shock, such as that resulting either from theexplosion of another charge in the vicinity of the controlled charge orfrom other undesirable vibrations set up in the water and reaching thecontrolled charge.

Still another object of my present invention is to provide improvedapparatus as above set forth which can be made either to expend itselfwhen striking the bottom of the ocean or not, as may be found mostdesirable.

A further object of my present invention is to provide an improvedmethod and apparatus of the type set forth both of which are extremelyeicient in operation, and the apparatus of which is very compact inconstruction and relatively inexpensive in cost.

In accordance with my present invention, I provide a heterodynedetecting device consisting of a magnetostrictionloudspeaker-microphoneoscillator unit provided with a vibratorydiaphragm and a three-quarter wavelength magnetostriction rod secured atone end to the diaphragm. At the two motional nodes of themagnetostriction rod, I couple a pair of coils thereto coaxially withthe rod, one coil constituting a driving or transmitting coil and theother a driven or receiving coil. The two coilsare connected to twovacuum tubes which, in turn, are connected in cascade, one tubereceiving its signal from the receiving coil, and the second tubereceiving its signal from the first tube, the second tube beingconnected so as to supply a signal to the driving coil. This circuit isarranged to oscillate at the frequency of the vibratorysystem comprisingthe magnetostriction rod and the vibratory portion of the diaphragm andintroduces an acoustic signal into the water through the diaphragm.

lf the singal emitted by the unit thus far described is reflected froman object moving relative thereto, the Doppler effect shift in thefrequency of the reflected signal will occur. Upon striking thediaphragm, the reflected signal will set up in the rod very smallvibrations which will regenerate around the oscillator circuit, therebyresulting in the detection of a heterodyne between the reected and theoutgoing signals. The heterodyne frequency will depend upon the relativespeed of the refleeting target or other object and the transducer unitabove described and will fall to zero at the minimum distance betweenthem. A selective amplifier and tiring circuit, set to fire theexplosive charge when some suitable low heterodyne frequency is reached,are connected to the output of the detector. An anticountermine switchis connected to the diaphragm and is suitably coupled to the ringcircuit to prevent firing of the charge when another charge detonates orsome other undesirable sonic vibrations appear in the vicinity of thecontrolled charge. The tiring circuit may be arranged so that,notwithstanding said switch, it will operate to re the charge when itstrikes the bottom of the ocean, or it may be arranged not to do so,depending upon whether or not it is desired that the controlled chargeshall re upon striking the bottom.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation, aswell as additional objects and advantages thereof, will best beunderstood from the following description of two embodiments thereof,when read in connection with the accompanying drawings, in which FIG. 1is a central, sectional view of one form of control apparatusconstructed in accordance with the present invention, certain of theparts being removed for the sake of clearness,

FIG. 2 is a top plan view of the apparatus with the cover shown in dashlines,

FIG. 3 is a wiring diagram of one circuit in accordance with the presentinvention, this circuit being useful when it is desired that the chargebe not fired upon striking the bottom of the ocean,

FIG. 4 is a wiring diagram showing a modied form of circuit useful whenit is desired that the charge be fired upon striking the bottom of theocean,

FIG. 5 is a circuit diagram of the limiter with reference to which itsoperation will be described in greater detail hereinafter,

FIGS. 6a and 6b are sets of curves showing instantaneous plate voltagevalues for various sine wave inputs to the limiter,

FIGS. 7a and 7b are curves showing the direct current components of thelimiter plate voltages corresponding, respectively, to the inputs of 6aand 6b,

FIG. 8 is a diagrammatic view illustrating the relation between afalling depth charge and a submarine target, and with reference to whichthe operation of the control apparatus of the present invention will bedescribed in greater detail hereinafter, and

FIG. 9 is a curve showing the response of the amplifier of the presentinvention.

Referring more particularly to the drawings, wherein similar referencecharacters designate corresponding parts throughout, there is shown inFIGS. 1 and 2, a control device 1 comprising a diaphragm 3 of magneticmaterial having a vibratory, central portion S coupled to the outerportion thereof by a thin, exible, annular portion 7 whereby the centralportion 5 is capable of acting substantially as a piston. Amagnetostrictive rod or the like 9 is secured to the vibratory portion 5of the diaphragm and forms therewith a vibratory system. The diaphragm 3is also provided with an annular recess 11 in which a casing or cover 13is received against a suitable gasket 15 to provide a water-tightconnection between the casing 13 and the diaphragm 3. The latter is alsoformed with a plurality of openings 17 through which suitable bolts maybe inserted for securing the device 1 to a depth charge or other similarexplosive 19, as shown in FIG. 8. Surrounding the magnetostrictive rodin coaxial relation therewith and in proximity to the diaphragm 3 is awinding 21 constituting a driving coil. An annular magnet 23 disposedabout the 'coil 21 is secured to the'di'aplragm 3 and supplies a biasingflux to the vibratory system. The flux path is completed by a yoke plate25 and a spacing member 27 disposed between the yoke plate 25 and themagnet 23. An alternating current magnetic shield 29 of copper or thelike is placed around the yoke plate 25, the spacer 27, the magnet 23,and the coil or winding 21.

Above the shield 29 is a cylindrical supporting member 31 which supportsa second coil or winding 33. The coil 33 is also disposed about and incoaxial relation with the rod 9 and acts as a receiving coil in a mannerto be presently described, the shield 29 serving to shield the coils 21and 33 from each other against induction. The space above the shield 29may also be utilized to compactly house the other components of thedevice to be presently described, and a suitable terminal plug 35 isprovided at the upper end of the casing for connection of thesecomponents to suitable power sources and the like. A gasket 37 of rubberor other suitable material is interposed between a flange on the plug 35and the casing 13 to provide a water-tight connection therebetween. Thecasing 13 may be secured in place by means of a pair of screws 39 whichare threaded into a pair of upstanding brackets 41 secured to thediaphragm 3 in any suitable manner.

The receiving or driven coil 33 is connected to the input circuit of apentode vacuum tube 43, such as a type 1T4 tube, which operates as acombined detector and amplifier. The output circuit of the tube 43 isconnected to the input circuit of a vacuum tube amplifier 45, such as atype 3A4 tube, the latter acting as a power amplifier. The driving coil21 is connected in the output or plate circuit of the power amplifier45. The arrangement is such that the vibratory system constituted by thepiston-like diaphragm portion 5, the magnetostrictive rod 9, the twowindings 21 and 33, and the tubes 43 and 45 form an oscillating circuitor system which generates the outgoing signal. The tube 43 excites thetube 45 which then drives the rod 9 through its output or plate coil 21,while the rod 9, in turn, excites the tube 43 through the receiving orgrid coil 33 thereof. This oscillatory system is arranged to oscillateat the natural frequency of the vibratory system comprised of thediaphragm portion 5 and the rod 9, and this frequency may beapproximately 25 kc. The length of the rod 9 is equal to three-fourthsof the wave length at the natural frequency of the oscillating system,and the windings 21 and 33 are preferably arranged about the rod 9 atthe two motional nodes thereof. In actual practice the rod 9 is, ofcourse, somewhat longer than three-fourths of the wavelength at thenatural frequency of the oscillating system so as to provide a short endbeyond its lower node region within the coil 21 for attachment to thediaphragm 3, as clearly shown in FIG. l.

The output of the tube 43 is also coupled to a three stage selectiveamplifier which includes a pentode 47, such as a type 1S5 tube, and apair of triodes 49 which may be enclosed in a single envelope, as in thetype 3A5 tubes. The output of the amplifier 49 is connected to a limiteramplifier 51 through a multi-stage, low-pass filter comprised ofresistors 53 and grounded capacitors 55 connected in tandem. A two-stagefilter of this type is shown in FIG. 3 by way of illustration. Theattenuation of the4 filter network 53, 55 increases as the frequency israised. Thus, to obtain a given output from the filter with risingfrequency, the input to the filter must be increased greatly as thefrequency is raised. The limiter amplifier 51 is of a type whichresponds only to signals of a voltage above a certain minimum. Hence,the input voltage to the filter network 53, 55 must be relatively highto obtain any limiter response. Now, the maximum voltage which can beapplied to the lter network is limited to the maximum output voltage ofthe amplifier tube 49 which drives it. As a result, there is a frequencydependent upon (a) the maximum output voltage of the driving tube 49,(b) the filter network 53, 55 and (c) the minimum voltage required tooperate the limiter 51 above which operation of the limiter cannot beobtained. This cut-off frequency, so to speak, may be selected at anysuitable or predetermined point and the filter network 53, 55 arrangedto pass on to the limiter amplifier 51 only voltages of a frequency lessthan said predetermined frequency for a purpose which will becomeapparent presently.

The output of the limiter amplifier 51, which may also be a pentode ofthe 155 typefis coupled through a network consisting of a resistor 57and a grounded capacitor 59 to a normally blocked, cold cathodedischarge device 61 which acts as a firing tube. The tube 61 may be atype 359A tube, for example. A capacitor 63 is connected in series withthe tube 61, as is also a detonator 65 associated with the depth charge19 in well-known manner. The capacitor 63 is normally charged through aresistor 66 from a suitable D.C. voltage source connected at the pointA.

Before proceeding with a description of the operation of the apparatusthus far described, it may be pointed out that the well-known Dopplereffect is employed to obtain ring of the charge at substantially thepoint of closest approach to the target, such as a submarine 67. Themethod of utilizing this effect will now be explained with reference toFIG. 8.

Assuming that the submarine 67 has been located, a depth charge 19 isdropped at a point as nearly over the submarine as can be judged. Whenthe charge has reached a certain depth below the surface of the water,pressureoperated switches therein function in a well-known mannerimmaterial to the present invention to close the various circuits to theseveral power sources indicated schematically in FIG. 3. As soon as theoscillatory system consisting of the diaphragm portion 5, themagnetostrictive rod 9, the coils Z1 and 33, and the tubes 43 and 45begins to function, the vibratory diaphragm portion 5 projects acontinuous, high frequency acoustical wave toward the submarine whichreflects the wave back to the diaphragm 3. This all takes place whilethe depth charge is moving relative to the submarine. Due to therelative velocity which exists between the depth charge 19 and thesubmarine 67, the received, reflected signal and the outgoing,transmitted signal will differ slightly in frequency, pursuant to theDoppler effect, the frequency difference depending upon the magnitude ofthe relative velocity between the charge 19 and the submarine 67.

If the angle 0 shown in FIG. 8 is the angle made at any instant betweena line from the depth charge 19 to the center of the submarine 67 andthe horizontal, f is the frequency of the transmitted signal, V is thedownward velocity of the depth charge 19, and C is the velocity ofsound, the difference frequency fd between the two signals at thatinstant is given by the expression As the device 1 of the depth charge19 passes by the submarine 67, the frequency difference fd will varyfrom a maximum value when the device first starts operating (forexample, cycles per second) to 0, the value 0 occurring at the instantof closest approach of the depth charge 19 to the submarine 67; that is,when the charge 19. and the submarine 67 are substantially both on thesame horizontal plane. This is the ideal point at which the chargeshould be tired. However, in practice, this is very diiicult to realize.Consequently, the charge is made to fire when the frequency differencefd is in the neighborhood of about cycles per second which correspondsto an angle 0 of about 11.5 from the horizontal.

Referring once more to FIG. 3, it will be seen that when thereiiectedsignal, which is extremely weak, is received bythe diaphragm portion 5,the rod 9 is caused to vibrate, thereby setting up weak signals in thereceiving coil 33. Signals generated in the coil or winding 33 are thenamplified by regeneration around the oscillator loop. Due to theregeneration, the amplitude of the received signal is sufficient toproduce a heterodyne on the grid of the tube 43. Thus, a component whosefrequency is the difference in frequency between the outgoing andreiected signals appears in the output of the tube 43, since this tubealso acts as a simple grid leak detector, as shown in FIG. 3. Thecircuit is designed so that the tube 43 will operate at maximum detectorsensitivity, while the tube 45 operates at maximum power output. It isfor this rea son that the two tubes 43 and 45 are employed instead of a`single tube in which either sensitivity or power would have to besacrificed.

The heterodyne signal representing the difference in frequency betweenthe transmitted and reflected waves is applied to the input of the tube47. The low pass filter 53, is designed to pass only very lowfrequencies. If desired or found necessary, the networks which couplethe various amplifier stages may be similarly designed more or less.Thus, when the frequency difference between the transmitted and receivedsignals is in the order of 30 cycles,` the signal is passed by theselective amplifier and is applied to the limiter tube 51. Thecharacteristic of this circuit is such that it will not respond at allto Weak signals, While its response to strong signals is independent ofsignal strength. This may be understood more readly from the followingdescription in connection with FIGS. 5, 6a, 6b, 7a and 7b:

The instantaneous value of the plate current of a tetrode or pentode isprincipally dependent on the instantaneous values of the control gridand screen grid voltages and is dependent only to a minor degree uponthe instantaneous value `of the plate voltage, provided this valueexceeds a certain minimum. If the value of the control grid voltage ecof the tube 51 be maintained at its constant zero signal voltage,increases in the screen voltage Es will result in nearly proportionatedecreases in the plate voltage ep, provided Es is not allowed toincrease beyond a certain limiting value. As Es approaches this limitingvalue, the plate current, ip, approaches its maximum value of ip(max.)=Ep/Rp. Thus, a value 0f Es may be found which reduces epsubstantially to zero. Further increases in Es will essentially produceno effect 0n ep. If Es is maintained at the minimum value required toreduce ep substantially to zero, and an alternating voltage ec beapplied to the control grid, the circuit acts as an average valuerectifier. During the positive portion of the cycle of ec, ep willremain at zero. During the negative portion of the cycle, ep will varyin proportion to ec. The direct current component of the plate voltagewill be the average value of ep, which will be porportional to theaverage value of eC rectified. FIGS. 6a and 7a show the result ofapplying a sine wave input to the circuit. For large `values of inputvoltage, the output D.C. voltage component is limited to the value 1/2E.

If the value of Es be set higher than the minimum value required toreduce the plate voltage substantially to zero in the absence of aninput signal, small amplitudes of input signal will produce no output,while the output for large inputs will be unchanged. An input largeenough to allow its negative peaks to compensate the excess of Es overthe minimum value is required to produce output. FIGS. 6b and 7billustrate the operation of this circuit with a sine wave input. Thiscondition of operation is employed in the heterodyne depth charge unitsaccording to my present invention.

It will be apparent from the foregoing description that the selectiveamplifier will pass on to the limited 51 only signals of a frequencybelow the predetermined frequency which is the high frequency cut-offfrequency of the filter network 53, 5S. It will also be apparent thatthe limiter 51 does not respond at all to the voltages supplied by theselective amplifier having an amplitude less than a predeterminedamplitude (for example, about 5 volts), whereas for voltages above thisamplitude, the tube 51 will respond. When these two conditions are met,the limiter tube 51 applies its output voltage pulses to the capacitor59, thereby gradually charging this capacitor. The network 57, 59 has atime constant of about 0.2 sec. after which the charged capacitor 59will fire the tube 61. As soon as the tube 61 is fired, there isprovided a current discharge path for the capacitor 63 through the tube61 and the detonator 65, thereby firing the charge 19.

In order to prevent premature firing of the charge 19 by extraneousnoises, such as that produced, for example, by the explosion of anothercharge in the vicinity of the controlled charge, there is provided ananti-countermine switch 6'9. This switch comprises a relatively stiffleaf spring 71 which is connected at one end to the diaphragm 3 or tosome other suitable member rigidly connected with the diaphragm. To theother end of the leaf spring 71 is connected a mass 73 which is tunedwith the spring 71 to some suitable frequency, say, for example,approximately 200 cycles per second. At one end of the mass 73 there issecured a second and relatively exible spring 75, the mass andresilience of which are also tuned to approximately the same frequencyas that at which the spring 71 and the mass 73 are resonant (say, within10 cycles per second thereof). The diaphragm 3 may be grounded and thespring 71, the mass 73 and the spring 75 are conductively connectedthereto. A terminal 77 having an adjustable terminal screw 79 thereon ismounted in insulated relation to the mass 73. Any abnormally intense,undesirable waves having a component frequency of the order of theresonant frequency of the switch 69 which strike the diaphragm 3 willcause the spring 71 and the mass 73 to vibrate at the resonant frequencythereof. This, in turn, will cause the spring 75 to vibrate at theresonant frequency, but with much greater amplitude, to contact thescrew 79 and thereby complete a circuit through a resistor 81 connectedto the capacitor 63 in shunt relation with the discharge tube 61 and thedetonator 65. Thus, when an abnormally intense wave strikes thediaphragm 3, the circuit through the resistor 81 is completed before theone through the discharge tube 61, and the capacitor 63 dischargesthrough the resistor 81 instead of through the detonator 65. In thisway, premature firing of the depth charge is avoided. If the source ofthe abnormal or undesired vibrations should be at a considerabledistance from the controlled depth charge 19, the amplitude of theabnormal vibrations striking the diaphragm 3 may be very small. It isfor this reason that the switch 69 is arranged as above described so asto greatly multiply the amplitude of vibration in the spring 75 andthereby insure engagement thereof with the terminal screw 79 to completethe alternative current discharge path through the resistor 81 for thecapacitor 63.

The design of the firing circuit in the heterodyne depth charge of mypresent invention is such that a definite time duration of firing signalis required before the circuit will fire the detonator. As the chargedrops in relation to the submarine, the frequency of the heterodynesignal applied to the amplifier input varies from its maximum value tozero, zero occurring at the instant of closest approach. The rate atwhich this frequency change is dependent on the distance from thesubmarine, being fast for a close approach and slow for a more distantapproach. The amplitude of the heterodyne signal applied to the input ofthe amplifier is greater for a close approach than for a more distantone. The frequency response curve of the amplifier, shown in FIG. 9, isdesigned so that these two effects tend to produce at the grid of thelimiter tube 51 a tiring signal for a length of time which is roughlyindependent of the nearness of approach to the submarine.

For a distant approach, the heterodyne signal is relatively Weak, andthe output of the amplifier is sufficient to produce firing only whenthe frequency is very near the peak of the response curve. For thisdistance, however, the frequency varies slowly, producing a firingsignal for the required length of time. For a close approach,

the heterodyne signal is very strong, and an amplifier output of firingamplitude is realized over a much wider range of frequencies, this rangebeing governed by the response curve. Since at this distance thefrequency varies much more rapidly, this additional range of frequenciesis required to provide the necessary time duration of firing signal. Theresponse curve is designed to provide a very nearly constant firingsignal time for all distances and to provide detonation at very nearlythe point of closest approach to the submarine.

Should there be no submarine or other target in the vicinity of thecharge 19, it is apparent that the charge will continue to fall until itreaches the bottom of the ocean where it will come to rest in the softmud. ln some cases, it may `be desirable to have the charge fired atthat point. For this purpose, the circuit shown in FIG. 4 may beemployed for coupling the output of the amplifier 49 to the limiter 51in place of the filter` network 53, 55. The frequency difference betweenthe signal transmitted to the ocean bottom and that reflected therebywhen the charge is close to the bottom may be of the order of 150 cyclesper second. With the filter network S3, 55 in the circuit as in FIG. 3,the heterodyne frequency is thus too high to cause firing of the charge,regardless of the signal strength, since this frequency is above thecut-off frequency described above. Now, with the filter network 53, 5Sremoved, as in FIG. 4, although the relatively high frequency heterodynesignal still may be greatly attenuated depending upon the frequencyresponse characteristic of the amplifier 47, 49, when the charge is veryclose to the bottom of the ocean (say, within two or three feetthereof), the signal strength of the heterodyne will be sufficient tocause the charge to be fired. In general, however, it is preferable notto have the explosive charge fired when it reaches the bottom of theocean because the waves which it then sets up in the water and thedisturbance produced by the gases generated thereby may interfere withreadings or other operations on board ship.

Although I have shown and described but two forms of my invention inconsiderable detail, it will be apparent to those skilled in the artthat many other modifications thereof as well as changes in the onesdescribed are possible. For eXatnble, the vibratory system need not belimited to one of the magnetostrictive type, but may be of any othersuitable type. Furthermore, even where the vibratory system is of themagnetostrictive type, the diaphragm 3 need not itself be of magneticmaterial, but may be made of non-magnetic material and a magnetic plateor the like secured thereto so as to provide a suitable flux returnpath. Also, in place Of the particular tubes specified above, othersuitable tubes may 'be employed. Other changes will, no doubt, readilysuggest themselves to those skilled in the art. I therefore desire thatmy invention shall not be limited except insofar as is made necessary bythe spirit of the appended claims.

I claim as my invention:

1. Apparatus for controlling the firing of an explosive chargecomprising a sonic transducer adapted to project sonic waves toward atarget and to receive sonic waves reflected back thereto from saidtarget While said transducer and said target move relative to eachother, the relative movement of said transducer and said targetresulting in a continually varying frequency difference between saidprojected and received waves in accordance with the Doppler effect andproducing in said transducer a correspondingly varying heterodynesignal, means associated with said transducer for detecting said varyingheterodyne signal, an amplifier coupled to said detecting means foramplifying said detected signal, and means associated with said chargecoupled to said amplifier and responsive to the output signal thereoffor firing said charge when said heterodyne signal has reached afrequency less than a predetermined frequency.

2. Apparatus according to claim 1 wherein said transducer comprises avibratory system including a vibratory diaphragm and magnetostrictivemeans secured to and movable with said diaphragm, and characterizedfurther in that said detecting means includes electron discharge meansforming with said vibratory system an oscillatory system, saidoscillatory system being arranged to oscillate at the natural frequencyof said vibratory system.

3. Apparatus according to claim 1 wherein said transducer comprises avibratory system including a vibratory diaphragm and a magnetostrictiveelement secured to and movable with said diaphragm, characterizedfurther in that said detecting means includes electron discharge meansforming with said vibratory system an oscillatory system, saidoscillatory system being arranged to oscillate at the natural frequencyof said vibratory system, and characterized still further in that saidmagnetostrictive element has a length substantially equal tothree-quarters of the wave length at said natural frequency.

4. Apparatus according to claim 1 wherein said transducer comprises avibratory system including a vibratory diaphragm and a magnetostrictiveelement secured to and movable with said diaphragm, characterizedfurther in that said detecting means includes electron discharge meansforming with said vibratory system an oscillatory system, saidoscillatory system being arranged lo oscillate at the natural frequencyof said vibratory system, characterized still further in that saidmagnetostrictive element has a length substantially equal tothree-quarters of the wave length at said natural frequency whereby saidelement has a pair of motional nodes, and characterized still further bythe addition of a pair of windings around said element, one at each ofsaid nodes, said windings being connected to said electron dischargemeans.

5. Apparatus according to claim 1 wherein said transducer comprises avibratory system including a vibratory diaphragm and a magnetostrictiveelement secured to and movable with said diaphragm, and characterizedfurther 1n that said detecting means includes a pair of electrondischarge tubes connected in cascade and a pair of windings eachconnected to a separate one of said tubes, said windings being disposedaround said magnetostrictive element at predetermined points thereon,one of said windings being connected in the output circuit of one ofsaid tubes and the other of said windings being connected 1n the inputcircuit of the other of said tubes.

6. Apparatus according to claim 1 wherein said transducer comprises avibratory system including a vibratory diaphragm and a magnetostrictiveelement secured to and movable with said diaphragm, characterizedfurther in that said detecting means includes a pair of electrondischarge tubes connected in cascade and a pair of windings eachconnected to a separate one of said tubes, said tubes and windingsforming with said vibratory system an oscillatory system and saidoscillatory system being arranged to operate at the natural frequency ofsaid vibratory system, characterized further in that saidmagnetostrictive element has a length equal substantially tothree-quarters of the wave length of said natural frequency whereby saidelement has a pair of motional nodes, and characterized still further inthat said windings are arranged coaxially around said element one ateach of said nodes.

7. Apparatus according to claim 1 wherein said transducer comprises avibratory system including a vibratory diaphragm and a magnetostrictiveelement secured to and movable with said diaphragm, and characterizedfurther in that said detecting means includes a vacuum tube detector anda vacuum tube power amplifier connected to the output of said detector,and a pair of windings arranged coaxially around said element atpredetermined points thereon, said detector and said power amplifiertogether with said pair of windings and said vibratory system forming anoscillatory system, one of said windings being connected in the outputcircuit of said power amplifier and constituting a driving winding forsaid vibratory system, and theother of said windings being connected inthe inputcircuit of said detector tube and constituting a receivingWinding in which signal impulses are generated by vibrations of saidvibratory system in response to the reflected waves received back bysaid diaphragm.

8.Apparatus according to claim 1 characterized in that said amplifierincludes a filter in the output circuit thereof adapt-ed to reject allfrequencies above said predetermined frequency.

9. Apparatus for controlling the firing of an explosive chargecomprising a sonic transducer adapted to project sonic waves toward atarget and to receive sonic waves reected back thereto from said targetwhile said transducer and target move relative to each other, therelative movement of said transducer and said target resulting in acontinually varying frequency difference between said projected andreceived waves in accordance with the Doppler eiect and producing insaid transducer a correspondingly varying heterodyne signal, meansassociated with said transducer for detecting said varying heterodynesignal, an amplifier coupled to said detecting means for amplifying saiddetected signal, a low pass filter connected in the output circuit ofsaid amplifier for passing only signals of a frequency below apredetermined frequency, a limiter connected `to the output of saidfilter for supplying voltage pulses, means in the output circuit of saidlimiter for storing the energy of said voltage pulses, and meansassociated with said explosive charge coupled to said storage means andresponsive to a predetermined voltage thereon for effecting firing ofsaid charge.

10. Apparatus according to claim 9 characterized in that said limiter isresponsive only to signals having an amplitude in excess of apredetermined minimum amplitude.

11. Apparatus according to claim 9 characterized in that `saidstoragemeans comprises a resistance-capacitance network having a predeterminedtime constant.

12.. Apparatus according to claim 9 characterized in that said firingmeans includes a normally blocked, cold cathode discharge device and anormally charged capacitor connected thereto, and characterized furtherin that said explosive charge includes a conductive charge detonatoralso connected to said discharge device, said discharge device beingadapted to be red in response to said storage means to provide a currentdischarge path for said capacitor through said detonator for ring saidexplosive charge.

13. Apparatus according to claim 9 characterized in that said firingmeans includes a normally blocked, cold cathode discharge device and anormally charged capacitor connected thereto, and characterized furtherin that said explosive charge includes a conductive charge detonatoralso connected to said discharge device, said dis- 10 charge devicebeing adapted to be red in response to said storage means to provide acurrent discharge path for said capacitor through said detonator forfiring said explosive charge, and characterized still further by theYaddition of means associated with said capacitor and providing thereforan additional current discharge path in shunt with said first namedpath, said last named means including a normally open circuit adapted tobe closed in response to abnormal waves whereby to provide analternative current discharge path for said capacitor to thereby avoidfiring of said explosive charge `in response to said abnormal Waves.

14. Apparatus according to claim 9 characterized in that said transducerincludes a vibratory diaphragm, characterized further in that saidfiring means includes a normally blocked, cold cathode discharge deviceand a normally charged capacitor connected thereto, and characterizedfurther in that said explosive charge includes a conductive chargedetonator also connected to said discharge device, said discharge devicebeing adapted to be fired in response to said storage means to provide acurrent discharge path for said capacitor through said detonator forfiring said explosive charge, and characterized still further by theaddition of means associated with said capacitor and providing thereforan additional current discharge path in shunt with said first namedpath, said last named means including a normally open inertia switchdevice connected to said diaphragm and means connecting said switchdevice to said capacitor, said switch device being adapted to be closed4 in response to abnormal Waves received by said diaphragm whereby toprovide an alternative current discharge path for said capacitor tothereby avoid tiring of said explosive charge in response to saidabnormal Waves.

References Cited UNITED STATES PATENTS 1,683,692 9/192s Ogden 102-71,780,592 11/1930 Johansson 102-7 2,319,107 5/1943 Brandt 20o-s22,325,908 s/1943 Edstmm 20o-52 2,060,198 11/1936 Hammond 114-212,193,361 3/1940 Rice 25o-1.25

VERLIN R. PENDEGRASS, Primary Examiner Us. c1. xn. 102-7,1s

1. APPARATUS FOR CONTROLLING THE FIRING OF AN EXPLOSIVE CHARGECOMPRISING A SONIC TRANSDUCER ADAPTED TO PROJECT SONIC WAVES TOWARD ATARGET AND TO RECEIVE SONIC WAVES REFLECTED BACK THERETO FROM SAIDTARGET WHILE SAID TRANSDUCER AND SAID TARGET MOVE RELATIVE TO EACHOTHER, THE RELATIVE MOVEMENT OF SAID TRANSDUCER AND SAID TARGETRESULTING IN A CONTINUALLY VARYING FREQUENCY DIFFERENCE BETWEEN SAIDPROJECTED AND RECEIVED WAVES IN ACCORDANCE WITH THE DOPPLER EFFECT ANDPRODUCING IN SAID TRANSDUCER A CORRESPONDINGLY VARYING HETERODYNESIGNAL, MEANS AS-